Modified methylol melamines and process of making and using same



Dec. 15, 1953 MODIFIED METHYLOL MELAMINES AND PROCESS OF MAKING AND USING SAME D. M. GAGARINE ETAL 2,562,872

Filed Oct. 2, 1950 409;, 9oz l I 20% nssmzr so". KL mans/u I g 1' Q g 12% 7g 70% I n-wv- STRENGTH INVHVTORS DM/l'k) u. GA 04010:, WILLIAM a. mum, m. a BY MIATLL' I JPAIYG'LEI? ATTORNEY-S Patented Dec. 15, 1953 MODIFIED METHYLOL MELAMINES AND PROCESS OF MAKING AND USING SAME Dmitry M. Gagarine, William B. Smith, Jr., and Myrtle J. Spangler, Danville, Va., assignors to Dan River Mills, Incorporated, a corporation of Virginia Application October 2, 1950, Serial No. 187,854

Claims.

This invention relates to imparting crease-resistance to cellulosic fabrics and more particularly to a water-soluble, thermosetting, synthetic resin which will produce this result on fabrics without lowering the tear strength of the fabric below a permissible minimum.

It has been known heretofore that the creaseresistance of fabrics could be increased practically to any desired extent by treatment of the fabric with a suitable synthetic resin, but the important practical limitation of that process has been the decrease which is simultaneously produced in the tear strength of the fabric as a result of the synthetic resin. For example, in typical prior art processes for imparting creaseresistance to fabrics, the tear strength would be decreased from 50% to 90% and the resulting cloth would be so weak in tear or tensile strength that it would not serve a practical purpose for use in ladies dress materials, mens shirts and the like.

In accordance with the present invention, the crease-resistance of the cloth may be increased as much as 70% to 100% and the tear strength not decreased more than about 30%. The synthetic resin with which we have been able to obtain these improved results comprises the reaction products of melamine, formaldehyde and urea, and although resins of this general type have been proposed heretofore for treatment of textiles, the above-described long-desired results of high crease-resistance accompanied by high tear-resistance have not been obtained with the prior resins. We have found from extensive re search on this problem that the reason for this failure, and likewise the reason for success in the use of the resin of our invention, is the necessity for a very critical control of the amounts or mol ratios of the three constituents.

We found that the desirable end results on the cloth can be obtained only if the above-mentioned three principal resin components are reacted in the mol ratios of 1 mol of melamine to 6 mols of formaldehyde to 3 to 4 mols of urea. It is this critical mol ratio that provides in the final resin the desirable characteristics, and if the amounts are varied substantially from these ratios the desirable high crease-resistance and high tear-resistance of the resin-treated cloth cannot be attained. For example, if more than 6 mols of formaldehyde are used, the tear strength of the fabric will be definitely diminished even though the desired crease-resistance of the fabric is attained. Similarly, but in reverse order, if the amount of urea is reduced substantially below 3 mols, the tear-strength of the cloth will be decreased and, on the other hand, if the amount of urea is increased substantially above 4 mols, the crease-resistance of the cloth will be diminished. Accordingly, to obtain the optimum results characteristic of our invention, the above ratios of 116:3 to 4 for the melamine, formaldehyde and urea, respectively, are critical and essential.

In preparing the above-described resin of our invention, we have found it advantageous to react the 1 mol of melamine first with the 6 mols of formaldehyde to produce hexamethylol melamine, and then react this intermediate product with the 3 to 4 mols of urea to produce the final resin. In addition to reacting the melamine with formaldehyde to produce the methylol product,

we have found it desirable to stabilize that methylolated product by treatment thereof with methyl alcohol or the equivalent to produce dimethyl ether of hexamethylol melamine. Without this ether modification, the finished resin has the objection of being unstable.

In preparing the hexamethylol melamine ether condensation product, we may start with straight melamine or with a melamine product which has already been partially methylated and methylolated, for example, the dimethyl ether of trimethylol melamine which is a commercially available product, and treat this with formaldehyde to produce the final hexamethylol product. In any event, sufiicient formaldehyde, namely 6 mols, is used to produce the hexamethylol condensation product and without any further,

methylolation.

Illustrative but non-limiting examples for producing the resin products characteristic of our invention are as follows:

The dimethyl ether of trimethylol melamine is first reacted with the3 mols of formaldehyde by mixing and heating the two ingredients, together with the sodium hydroxide which acts as a catalyst, to 157 F. for 15 to 20 minutes. This produces the dimethyl ether of hexamethylol melamine, which is then reacted with the urea by =3 heating the mixture thereof to 145 F., followed by cooling of the reaction product and storing in drums.

EXAMPLE II Mol Constituents Amount Mols ratio Dimethyl ether of trimethylol l,750lbs 5. 7S 1.

melamine (80% water solution). Formaldehyde (37% water solution) 1,400 lbs.- 1T. 2 3 Urea (dry compound) 1,150 lbs 19. l 3. 33 20% sodium hydroxide 2,800 mls... Concentrated hydrochloric acid.. 1,200 mls;

The dimethyl ether of trimethylol melamine is first reacted with the 3 molstof formaldehyde- III Constituents Amount Mols ratio Melamine 17251135 5. 7s 1 Formaldehyde (37% water solution); 2,800 lbs... 3414 6 Methyl alcohol. l,800 lbs 57. 3 10 20% sodium hydroxide 1,400 rnls- Concentrated hydrochloric'acid 600 mls In this example, melamine is used: as one-of the starting materials and is'reacted with the 6 mols of formaldehyde toformthe hexamethylol product,. which is then methylated with the methylalcohol to producetthe methylether of hexamethylol melaminea More, specifically, the melamine, formaldehyde and sodium. hydroxide are heated together to- 150? until thehexamethylol' derivative is formed. The. methyl a1- cohol is then added, and the solution acidified with hydrochloric acid until the pH isbetween 4 and 5:. The, solution is then' heated. until-;the dimethyl ether. is formed-and theexcess methyl alcohol distilled on. The large excess of methyl alcohol. is necessary toinsure the reactiontaking place.

EXAMPLE IV' Mol Constituents Amount Mols ratio -Dimethyl etherof trimethylol- 1,750lbs 5.73 l

melamine (80% water solution). Formaldehyde (37% \vatersolution) 1,400 lbs Dicyandiamide (dry compound)... 1,450 lbs Sodium hydroxide (20% solution)" 1,400 lbs-.-"

In this example, dicyandiamide is used in place of urea but the-process is generally the same as that described above in connection with the preceding examples; that is, the dimethyl etherof trimethylol melamine is heated with formaldehyde to 150 F. to-form the hexamethylol derivative, and this intermediate condensation product is then reacted with the dicyandiamideby heat- 4 ing to approximately 170 F. to produce the final reaction product.

The resin prepared in accordance with the above formulas and procedure has definite chemical characteristics which make it suitable for obtaining the desired crease-resistance and tear strength incloth to which-the resin is applied, particularly in terms of the degree of polymerizat-ion and the consequent degree of potential reactivity of'. the resin with the cloth, which may be constructedof any desired type of cellulosic fibers, such as, for example, cotton, rayon and linen; We-have found the process of our invention to have substantial commercial value when appliedtoladies dress materials and mens shirting materials made of cotton or viscose rayon onmixturesthereof. The resin is water-soluble and may be applied to any of these cellulosic fabrics in an aqueous solution. The resin is normally substantially neutral, but should be made weakly acid to effect. proper reaction with the cellulose of the cloth; For this purpose an acid catalyst/such as the-amine hydrochloride catalyst manufacturedby Monsanto Chemical Company and sold" under the trade name AC is used. After application of the resin containing this catalyst to the cloth and heating; the catalyst turns the resin slightly acid; which catalyzesthe polymerization of the resin andits'reaction with the cellulose of the cloth:

Typical crease-resistance and tear strength characteristics of cotton gingham are illustrated by thecurves in the accompanying drawing. It can be seen that by using varying amounts of the Resins Nos. I and-"II, which wereproduced in accordance'with Examples I and II above; the crease-resistance" increases fromto- 93%, while the tear strength decreases from- 100% to 40%. The curves show that thegreater the amount of resin used; the greater is the creaseresistance, but the lower is the tear strength.

In these curves, complete'recovery from creasing (which is neverattained in actual practice) is called 100%. Also, the tear strength of the untreated cloth is listed as 100%. v In usualcomm'ercial practiceit is desirable to have an' in'crease in crease-resistancesuch as indicated'by'the' use of 10 to- 20% of Resin-Tor II'an'd' alsonotito have the tear strength of the fabric decrease more than the corresponding values for this concentration. More specifically, the two curves for Resinsl? and II' in'the accompanying drawing. show the following data for crease resistanee and, tear strength when the amount of resin used varies from 0 to'40% dry resin based on the weight of the'cloth'.

RESINYI- Concentration}. percent dry solidsi based Tear Creaseon weight of cloth. strength resistance Percent Percent 100 55 90 67 80 67 82 50. 88 40 01 dehyde, ketone formaldehyde, melamine formaldehyde, other thermosetting formaldehyde condensation productseven formaldehyde itself has been used. These have all been applied to cellulosic fabrics in aqueous solutions and thereafter polymerized to an insoluble state by heating under acid conditions. All of the above-mentioned products have a methylol (CHzOH) group and it is believed that the OI-I radical of the methylol group reacts with an H atom of the hydroxyl group of a cellulose molecule, splitting off water and chemically combining the resin molecule and the cellulose molecule. By having a single resin molecule react with two or more cellulose molecules, the cellulose molecules are cross-linked to form a fairly rigid, three-dimensional net-work. This is illustrated below where a resin molecule with two methylol groups attached to a resin nucleus R serves to cross-link two cellulose molecules z -o --z where OH shows the position of one of the hydroxyl groups in the cellulose molecule and shows the remainder of the cellulose molecule.

2 --o --z Hon R HCH Z -t -z B011 2 -o o HCH H H z -----oz HoH R HCH z --o --o --z HOE R The very rigidity which gives resistance to bending does not allow the cellulose fibers to distribute the tensile stresses, and materially lowers the tear and tensile strength.

If we can maintain this three-dimensional configuration and at the same time make the system more flexible, we will maintain the crease-resistance and regain some of the loss in tear and tensile strength. This can be done by making the resin cross-linkages between the cellulose molecules longer and more flexible. Compare the illustration below showing this type of cross-linking with the shorter, relatively inflexible crosslinking shown above.

R HCH Z --O -O --Z HOH R HGH R HCH R HGH R HCH Z O O Z HCH R HCH R HCH R HCH R HCH Z --O --O -Z HCH R We have discovered that to obtain this flexible resin cross-linkages, it is necessary to have a certain definite ratio of functional groups within the resin molecule. The ratio which we have found to be satisfactory is at least 2 labile hydrogens to 1 methylol (or equivalent) group. The methylol (or equivalent) group is that functional group which reacts with the hydroxyl group of the cellulose molecule. It is, furthermore, the reaction between the labile hydrogens and the methylol (or equivalent) group which causes the polymerization of resin molecules from low molecular weight monomers.

In so far as We know, this ratio of labile hydrogens to methylol (or equivalent) groups has never been known or understood; nor do any of the prior art resins possess this ratio of labile hydrogens to methylol (or equivalent) groups.

By having this ratio of functional groups within the resin molecule, we accomplish the followmg:

(A) A resin molecule in a low state of polymerization reacts with a cellulose molecule as shown.

(B) Because of the large excess of labile hydrogens on adjacent resin molecules, the resin molecules polymerize, growing larger, longer and more flexible, as shown below.

film'thermoreriit .islthe reactioninbatween" the hbile hydro'genstzandzzthe radicalilofzzthe 'methylollgroupsithaticauses theLresin-limolecnles to polymerize into.relatively zlarzgegwateri nsolu- -ble molecules.

5 Theabove' theorymayzperhaps belbetterzunder- "stood by reference to. the; following illustrationlof the chemicalreaction .which :is sbelievedttoetake place whentthe resin acomponentsaoftExamplei I above are reacted:

Dlmethyl ether of trimethylol melamine Formaldehyde H H O O f HO-H2C-N-CH2-O-CH3 Dimethyl ether of hexamethylol melamine When this intermediate condensation product,

that is, the dimethyl ether of hexamethylol melamine, is reacted with 3 mols of urea as described Example I above, the following tYpeoi-resinousmroduct-results:

It cam-be-seen from *the abovethat the resin hasone methylol group and two methylol methyl -'ether-groups which are the equivalent of-*methylol groups in that they undergo the samereactions-i at -a slightly 1 higher temperature; 'six primary amino hydrogens; and three secondary amino hydrogens, all of which are labile. This isthen the :ratio'of three labilediydrogens to one 1 methyloi group.

" tion.

We 'claim: 1. A process of producing-a-water-=soluble, thermosetting, synthetic resin. forming material suitable for treatment'iof cellulosidfabrics to pro-,-

vide crease-resistance in the 'fabric and with limited-decrease in. the. tear. strength oithe fabric,

.lcomprising reacting 1 mol of. melaminewith 6 -mols of formaldehyde to .produce -hexameth ylol melamineand reacting that product .w'ith13' to 4- mols of urea, the reaction with the urea. being completed in the presence of an amount of acid suflicient to react all urea with the hexamethylol melaminebut insufficient to convert: the reaction product to the infusible and insoluble state.

2. A process of .pr.oducing a water-soluble, thermosetting, synthetic resin forming material suitable for vtreatment'of 'cellulosic fabrics to provide crease-resistance in .the :fabric and with limited'decrease in the tear strength ofithe fabric, comprising reacting 1 molliof melamine with 6 111015 of formaldehyde .to produce hexamethylol melamine, stabilizing said hex'amethylol" melamine by reacting with methyl alcohol, and then .reacting this stabilized hexamethylol melamine with 3 to 4 mols of urea in the. presenceofan acid under such conditions as will completely react up to 4"molsiof urea with said hexameth'ylol'melamine but in an amount ins'ufficient toinsolulbilize the reaction product.

" 3.. A process of increasing the crease-resistance of cellulosic" fabrics. accompanied by .only'limited "reduction in. the tear'strength'of the fabric; com- ;prising applying to'the fabric anacid'reacting vzgocatalyst andnaqueous solution of athermosetting Synthetic resin forminglmaterial composed .'.'of the reactionpr'oducts 'of l moliof a hexameth- .ylol melamine and 3 to'. 4.,mols of urea, heating lithecloth. treated with this resin forming material i .25, .to effectpolymerization and reaction thereof with thecellulose .of' the fabric.

. 4. A cellulosic" fabric having relatively high crease-resistance and tear strength, impregnated and reacted with a thermosetting synthetic resin composed of thereaction' products a hexamethylol melamine reacted with from 3 to 4 mols of curea, under such. conditions.that-..all. free ureais reacted. with themelamine.

5. A water-soluble, thermosetting, synthetic resin forming material, consisting of the reaction product of 1 mol of hexamethylol, methylated melamine and 3 to 4'mols of urea, said resin forming material beingadaptedto -.be. applied to textile fabrics \for l increasing .the, crease-resistance thereof While retaining the necessary tear strength of the fabric.

""6: A non-free urea containingwater-soluble, thermosetting, monomeric, synthetic resin forming material, consisting of the reaction product of 1 mol of dimethyl ether of trimethylol melamine, 3 mols of formaldehyde and 3 to 4 mols of urea, said resin forming material being adapted to be applied to textile fabrics for increasing the crease-resistancethereof 'while retaining the necessary tearstrength of the-fabric.

"7. A' process of "producing -a water-sohible, thermosetting, -synthetic resin= forming material,

comprising reacting 1 mol of melamine-with 6 mols of formaldehyde and Zmols-of methyl-alcohol to' produce the dimethyl ether -ofhexamethylol melam-ineg and then'reacting- 1-m'ol='of this di- 'methyb-ethei ofhexamethylol me1amine' w'itli' 3 to 4'm'ols of urea; undermildacid conditions.

a; 8. A pro'cess of"- producing awaterrs'oluble, thermosetting, synthetic resin -forming material, comprising reacting 1 mol of dimethyl- 'ether of trimethylol melamine with 3 mols of formaldehyde to produce the dimethyl ether of hexamethylol'melamine and then reacting 1 mol of said dimethyl ether of hexamethylor melamine with 3 to 4 mols of urea under acid zconditions.

9;The process Of-prOducing-a water'soluble heat-setting resin-forming material which comprises reacting 1 mold a hexamethylol melamine with from about 3 to 4 mols of urea, the reaction conditions being such that all free urea is combined with the hexamethylol melamine.

10. A water soluble reaction product of 1 mol ..-of. a. hexamethylol melamine and from about 3 characterized by the absence of any free urea and by its ability to produce a high degree of crease resistance with a minimum reduction in before strength when applied to cellulosic textile fabrics and. polymerized in situ.

DMITRY M. GAGARINE. WILLIAM B. SMITH, JR. MYRTLE J. SPAN GLER.

References Cited in the file of this patent Number 2,328,424 2,456,568 2,466,457 2,504,857 2,545,450

Number UNITED STATES PATENTS Name Date D'Alelio Aug. 31, 1943 Scott Dec. 14, 1948 Lynn Apr. 5, 1949 MacIntyre Apr. 18, 1950 Dalton Mar. 20, 1951 FOREIGN PATENTS Country Date Great Britain May 17, 1949 

5. A WATER-SOLUBLE, THERMOSETTING, SYNTHETIC RESIN FORMING MATERIAL, CONSISTING OF THE REACTION PRODUCT OF 1 MOL OF HEXAMETHYLOL, METHYLATED MELAMINE AND 3 TO 4 MOLS OF UREA, SAID RESIN FORMING MATERIAL BEING ADAPTED TO BE APPLIED TO TEXTILE FABRICS FOR INCREASING THE CREASE-RESISTANCE THEREOF WHILE RETAINING THE NECESSARY TEAR STRENGTH OF THE FABRIC.
 6. A NON-FREE UREA CONTAINING WATER-SOLUBLE, THERMOSETTING, MONOMERIC, SYNTHETIC RESIN FORMING MATERIAL, CONSISTING OF THE REACTION PRODUCT OF 1 MOL OF DIMETHYL ETHER OF TRIMETHYLOL MELAMINE, 3 MOLS OF FORMALDEHYDE, AND 3 T 4 MOLS OF UREA, SAID RESIN FORMING MATERIAL BEING ADAPTED TO BE 